This invention relates to a high pressure fuel feeding device for a fuel injected engine and more particularly to numerous improvements in such engines.
The advantages of high pressure fuel injection in the charge forming systems for internal combustion engines are well acknowledged. Fuel injection offers better control of the fuel/air mixture and also permits control of the position of the fuel/air charge in the combustion chamber at the time of ignition so as to permit stratification at low and part loads. Thus, there are particular advantages both for exhaust emission control and fuel economy to provide high pressure fuel injection systems. However, in order to provide such systems there are a number of factors which must be considered. For example, the use of fuel injection normally employs additional components to those of normally carbureted engines such as high pressure fuel pumps and pressure regulators. In order to add these components to the system, not only does cost become a factor but also the actual physical location of the components can present a problem. In addition, as further components are added to the system, the problem of possible leakage becomes significant.
It is, therefore, a principal object of this invention to provide an improved high pressure fuel injection system for an internal combustion engine wherein the number of connections and external components can be reduced.
One form of fuel injection system which is of considerable interest injects not only fuel but high pressure air into the engine. Such "fuel/air injectors" have some advantages over conventional fuel injectors. However, the addition of high pressure air to the high pressure fuel gives rise to additional problems in complexity. This is particularly true in view of the fact that the air pressure must be regulated as well as the fuel pressure.
It is, therefore, a still further object of this invention to provide an improved fuel/air injection system for an internal combustion engine.
One specific application for internal combustion engines wherein fuel and/or fuel/air injectors may have some interest is in outboard motors. Outboard motors frequently utilize two cycle internal combustion engines as their power plant due to the simplicity and high specific output of such engines. However, the exhaust emission control for such engines is also well known to be a substantial problem. The use of fuel and/or fuel/air injection for such engines may be useful in reducing exhaust emission control.
However, the problems as aforenoted with fuel injection and/or fuel/air injection systems become further complicated in connection with outboard motors. Specifically, an outboard motor requires an extremely compact arrangement and this further complicates not only the positioning of the various components but the insurance of effective sealing.
It is, therefore, a still further object of this invention to provide an improved injection system for an outboard motor.
In the co-pending application entitled "High Pressure Fuel Feeding Device For Fuel Injected Engine", Ser. No. 959,684, filed Oct. 13, 1992 in the name of Naoki Karo and assigned to the Assignee hereof, there is disclosed a high pressure fuel injection system for an outboard motor that avoids many of the difficulties of the prior art type constructions previously referred to. It is a further object of this invention to provide certain specific improvements over the systems shown in that application.
Specifically, that patent application discloses an arrangement wherein there is a fuel vapor separator positioned in the fuel supply system upstream of the high pressure fuel pump and which functions to separate vapors from the fuel. In that application, there is also provided an air pressure regulator and the air pressure regulation is achieved by dumping excess air pressure back to the fuel vapor separator and this will insure against the discharge of fuel vapors, which can become mixed with the air in the fuel/air injection system from being discharged to the atmosphere.
It is a further principal object of this invention to provide an improved fuel vapor separator arrangement and air compressor pressure regulation system wherein the air pressure is regulated by dumping air back to the fuel vapor separator and additional separation of fuel from the returned air in the fuel vapor separator is accomplished.
It is a further object of this invention to provide an improved fuel vapor separator for an fuel/air injection system for an internal combustion engine wherein the fuel vapor separator also processes the air which is delivered to the air compressor of the fuel/air injection system.
In the fuel vapor separator shown in the aforenoted copending application, the excess air which is dumped from the air pressure regulator is delivered to an air chamber which in turn communicates with the fuel vapor separator through a return conduit through which condensed fuel may return. However, such an arrangement may not be as fully effective as desirable in insuring that the maximum amount of fuel can be separated from the returned air and returned to the fuel vapor separator.
It is, therefore, a still further object of this invention to provide an improved fuel vapor separator for a fuel/air injection system wherein the air compressor of the engine has its pressure regulated by dumping excess air directly back to the fuel vapor separator through a perforate member which will insure complete separation of any fuel from the bypassed air.
As has been noted, it is extremely important, particularly with such applications as outboard motors, to provide a very compact assembly and nevertheless one which can be easily serviced. The construction shown in the aforenoted co-pending patent application provides a fuel vapor separator with the air pressure regulator and the fuel pressure regulator being positioned in close proximity to the fuel vapor separator and thus provides a compact assembly. However, the arrangement shown in that application requires a number of external conduits and these can provide leakage problems, as aforenoted.
It is, therefore, a still further object of this invention to provide an improved and compact fuel vapor separator, fuel pressure regulator and air pressure regulator for a fuel/air injection system for an engine which is compact in construction and which minimizes the number of required external components.
In the arrangement shown in the aforenoted co-pending application, the air for the air compressor is drawn at least in part from the fuel vapor separator. However, in that application the air component of the fuel vapor separator is separate from the fuel reservoir and this gives rise to certain problems, some of which have been aforenoted. In addition, with such a separate location it is not possible to provide the desired amount of air filtration as may be required.
It is, therefore, a still further object of this invention to provide a fuel vapor separator system for a fuel/air injection system for an internal combustion engine wherein the air and fuel chambers of the separator are positioned in close proximity to each other and wherein the air chamber is filled with a filter media for filtering air which is supplied to the air compressor of the system.
As has been previously noted, one desirable application for fuel/air injection systems is in outboard motors because of their normal use of two cycle engines as power sources. However, in addition to the problems as aforenoted, outboard motors provide a number of additional problems in connection with design and operation. For example, in an outboard motor it is common to adjust the trim of the outboard motor during operation. Trim adjustment normally is accomplished by means of pivotal movement about a horizontally disposed trim axis and this change in inclination of the engine and its associated components can give rise to certain problems.
For example, if the engine employs a fuel vapor separator and air is returned or drawn from the air chamber of the fuel vapor separator, inclination of the outboard motor can cause fuel to enter the air chamber and pass through one of the air passages. This is obviously undesirable. This problem is particularly acute when it is considered that the outboard motor may be detached from the associated watercraft and laid down while still having fuel in its system.
It is, therefore, a still further object of this invention to provide a fuel vapor separator for an outboard motor wherein the air portion of the separator can supply air to an air compressor and it will be insured that fuel cannot enter the air system.
As has been previously noted, systems of this type and those shown in the aforenoted co-pending application draw the air from the air compressor from the air chamber of the fuel vapor separator. Although this has the advantage of insuring that fuel cannot be discharged to the atmosphere, it may be that the amount of air supplied to the air compressor through such systems may be inadequate.
It is, therefore, a still further object of this invention to provide an improved fuel/air injection system for an internal combustion engine wherein adequate air is supplied to the air compressor under all running conditions.
As has been previously noted, when fuel/air injection systems are employed it is necessary to regulate both fuel pressure and air pressure. However, if the fuel pressure and air pressure are regulated independently of each other, this can cause undesirable variations in the fuel/air ratio.
It is, therefore, a further object of this invention to provide an improved pressure regulating system for air/fuel injector wherein the fuel and air pressures are both regulated and wherein the difference between the fuel and air pressure is also regulated.
In systems of the type described and particularly those in the aforenoted co-pending application wherein the system is at east partially closed in that the air and fuel are both contained within a common air/fuel separator, there can be a problem. If for some reason the supply of fuel is discontinued and high pressure air is still supplied to the air/fuel injector, this high pressure air can act back through the system and cause the undesirable discharge of fuel.
It is, therefore, a still further object of this invention to provide an improved fuel/air pressure regulating system wherein the supply of air under pressure will be discontinued in the event fuel pressure falls below a predetermined desired amount.
In addition to the problems as aforenoted, there are still additional problems in conjunction with fuel/air injection systems that are particularly acute in connection with outboard motors. As has been previously noted, with outboard motors the construction is quite compact and certain of the components are mounted directly on the engine. This means that engine vibrations can be transmitted to those components and cause undesirable results. For example, the fuel vapor separator normally employs a float operated valve and the vibrations if transmitted to the valve can cause malfunctions. In addition, the vibrations can cause weakening of the various air and fuel connections.
It is, therefore, a still further object of this invention to provide an improved arrangement for an fuel/air injection system for an engine wherein certain of the components are mounted resiliently or are themselves resilient so as to reduce the adverse effects of vibration.